Apparatus for and method of exciting electric oscillations.



E. L'. CHAFFEE. APPARATUS FOR AND METHOD OF EXCITING ELECTRICOSCILLATIONS. APPLICATION HLED NOV. 4, I911. 1,189,791. PatentedJuly4,1916.

2 SHEETS-SHEET I.

/ e & j

E. L. CHAFFE E. APPARATUS FOR AND METHOD OF EXCITING ELECTRICOSCILLATIONS.

; APPLICATION FILED NOV. 4, I91]. 1,189,791.

Patented July 4, 1916.

2 SHEETS-SHEET 2- ,a'zmssea EMORY LEON onnrrnn, or SOMERVILLELMASSACHUSETTS, AssIeNon', BY rimer AND MESNE ASSIGNMENTS, T FULTONcomma, or 'ruxnno PARK, NEW YORK.

APPARATUS FOR AND METHOD OF EXCITING ELECTRIC OSGILLATIONS.

Specification of Letters Patent.

Patented July a, 1916.

Application filed November 4, 1911. Serial No. 658,539.

To all whom it may concern:

I Be it known that I, EMORY LEON CHAF- FEE, a citizen of the UnitedStates, and resident of Somerville, in the county of Middlesex and Stateof Massachusetts, have invented new. and useful Improvements inApparatus for and Methodsyof Exciting Electric Oscillations, of whichthe follow- Arts and Sciences, Vol. XLVII'No. 9, No

vember, 1911, page 267.

The object of my invention, which practical demonstration proves to havebeen attained, is to provide in a high degree of perfection uniform andregular electric oscillations of small damping .and large trainfrequency, and, moreover, to provide such oscillations by means of asimple, economical and continuously reliable apparatus, which operateswith freedom from inherent vibrations of audible frequenty, and istherefore applicable to any uses where such oscillations are required;particularly to radio-telephony. The fact that by the apparatus andmethod, presently herein to be particularly described, there have beenobtained continuous, practically undamped oscillations of severalamper'es at twenty meters wave length, corresponding to a frequency of1.5xl0 oscillations per second, sufliciently suggests the utilities towhich my invention may be applied.v

In the drawings hereto annexed, which illustrate my invention, Figure lis alongitudinal elevation, partly in section, of a discharge-gap; Fig.2 is half end elevation, half cross section at the line 2, 2 of Fig. 1;Fig. 3 is a diagram, showing a mode of connecting the discharge-gap in aradio-telephonic system; Fig. 4 is a diagram showing ,an alternativemethod of connection, foro b g taining an increased power-output; Fig. 5is a diagram showing another alternative method of connection, for thesame purpose; Figs. 6 and 7 are diagrams illustrating the action of thedischarge-gap, and the relation between exciting impulses and excitedoscillations.

The apparatus.The discharge-gap, indicated comprehensively in Fig. 3 bythe letter G, is shown in detail in Figs. 1 and 2.

The electrodes or terminals, e, e, are mean lic plugs tapered to fittightly in the bores of relatively massive metallic supports t, t. Thesesupports are preferablyribbed as at D, D, and blackened, so as freely toradiate heat. The supports t, t are threaded into tapped holes in themetal plates 0, e' which are separated and insulated by a centrallyperforated slab b, of hard rubber, asbestos board, or other adequateinsulating material- Insulating knobs 7', 'r are provided for adjustmentof the supports 25, t, and consequently the electrodes or terminals e,e. Binding posts P, P serve for connecting the discharge-gap in theelectrical system, and pipes a and 0 provide inlet and outletrespectively for hydrogen or hydrocarbon gas, to maintain an atmosphereproductive of an advantageous volt-ampere characteristic, surroundingthe discharge.

This atmosphere of hydrogen or hydrocarbon, if moist, as is preferable,also probably has a chemical action upon the electrodes.

The electrodes e, e are composed of dis similar metals, of such acharacter and so disposed that when the apparatus is active,

a much larger discharge current passes across thegap in one directionthan in the opposite. The best discharge-gap construction known to --meat present is one in which the cathode is a highly oxidizable metal, forexample, aluminum and the .anode copperor silver,a node.and cathodebeing determined with reference to a unidirectional source of current 1nthe circuit which includes the discharge-gap; the separation between thetwo electrode faces being quite small, say about .07 mm. The area ofeach] electrode face may conveniently be sp arsquare cm., and the twofaces should be accurately parallel and smooth; While the abovespecifications express the preferred condition, an alloy ofaluminum, ormagnesium, or an alloy of magnesium, or an alloy composed of aluminumand mag: nesium, or-a'mixture of alloys of the two metals, will produceeffects the same in kind as those obtained with the preferred alu'-minum electrode. While copper or silver .is preferable for theanode-material, the metal of which the anode may be composed may be verywidely varied without seriously interfering with the correct andeflicient op eration of the discharge-gap.

The rectification-effect in such a discharge-gap as above described. isbelieved to I be due, first: to the practically instantaneousreestablishment of the high initial gapresistance when the currentbecomes zero, probably because of the formation of a film of insulatingmaterial, probably an oxid on the aluminum or equivalent terminal; sec-0nd: to the higher cathode-drop of the anode-metal, and third: to theabsorption of energy by the secondary. The existence of the insulatingfilm is plainly evident upon an aluminum terminal which .has been in usefor a short time in the gap, and is seen upon a removed terminal as avery hard black coating which tests show to be practicallynon-conductive of electricity.

' This film probably assists the. rectification by its alternatereduction by the hydrogen and subsequent oxidation by the oxygenintroduced with the original aluminum or which is introduced by moisturecarried in with the hydrogen.

Figs. 3, 4 and 5 illustrate modes in which the above describeddischarge-gap may be associated with the components of an oscil- Jlating system. Referring especially to Fig.

3: T represents an oscillation-transformer,- shown as inductivelycoupled. D C repre- -sents a direct current source-of say 400 to 500volts more or less-connected with the discharge-gap G througha. supplycircuit including the series resistance R andseries inductances L L. Crepresents a condenser, connected; across the circuit, 'P is the primarycoil and S the secondary of the oscillation transformer T. The condenser.C and primary coil P form withthedischarge-gap G, an exciting circuitwhich is metallically closed except for the space of the gap, and thedielectric of the condenser. The secondary coil S isconnected to theantenna A, and toground; a telephonetransmitter Msay, -'of themicrophonic the secondary coil S. Other modes of in-' type,is insertedas shown in the oscilla tionor'radiating circuit which; comprisessorting the telephone are well known, andv maybe'employed alternatively,so long as.

I the. telephone s il -such position as to vary together with the maincurrent which prethe current flowin in the antenna by the imposition ofperlodic undulation having. the characteristic of articulate speechFigs. 4 and 5 need not be described at length. They indicatearrangements of discharge-gaps either in series or in parallel for thepurpose of obtaining a greater power-output. I I

Adjustment of the apparatus, and the method of 0pemtz'0n.-The circuitsrepresented by Fig. 3 (likewise Figs..4 and 5) ,may 'be adjusted toarelation which insures 'efiicient operation, by variation of one ormore of the quantities represented by R, P, C or S. This adjustment is,however, not such as to produce equivalent or approxi-' matelyequivalent time-periods of the primary and secondary oscillationcircuits, butis a novel adjustment, functionally significant in theeffective operation of this 0 invention, and an important characteristicof the new method herein described. This novel adjustment may beexplained by reference to Figs. 6 and 7. I

Figs. 6 and 7 are diagrams in which the ordinates represent current andare plotted against abscissae representing time. "The heavily drawncurve I represents-the current in the primary or exciting circuit (C, P,G, Fig. 3,) and the lightly drawn curve 1*, the current in the secondaryor oscillation circuit, (A, S, M, 'Fig. 3). Both of..these curverepresentations are approximate. The current I" in the primary circuitconsists of recurrent rectified impulses, in each of which currentbuilds up-to a reverse to an opposite maximum. Tracing the recurrencesfrom their beginning: The potential of the condenser C reaches a valuesufficient to overcome the discharge-gap resistance; then, on beingovercome, the gapresistance falls to a very low. value; and thereuponthe discharge of the condenser viously charged the condenser, rushesacross the gap and through the primary coil P. At the end of thiscurrent-rush the current through the gap is zero, and the condenser hasan inverse charge; the main current from the source D 0 thereuponneutralizes chargesit in the initial direction, increasing the condenserpotential until the gapresistance again breaks down. During the"interval between successive primary dis-.

primary, continues to oscillate in its own free period, with suchdamping as is inevitably dueto the conditions ofthe sec- 125 ondarycircuit (regarded solely) such as resistance and radiation. -Although,for this reason,,- the secondary oscillation cannot strictly be Icharacterized as absolutely un charges thesecondary, excited by the a I(Fig, 3) can attain higher potentialsthan damped, it can be maintainedinsubstantial constancy bycausing the primary exciting impulse to recurat time intervals which are integral multiples of the time-period of thesecondary oscillation, and in such phase relation Withthe secondaryoscillation that each primary excitation comes in to maintain andamplify the declining secondary oscillation. By so re'newihg theexcitant eifect, the secondary oscillation becomes practicallycontinuous, uniform, and undamped. By virtue of the inductances L, L,inthe source-circuit, the condenser C the source itself; the maximumcondenser potential is determined by the breaking down potential of thedischarge-gap G. This. may be assumed to be constant, or practically so;thus the number of discharges per second depends upon the supply currentand the condenser.

on account of the definite, thoughdistorted, form of the primaryimpulse, and

" the resulting impulse of electromotive force that. the primary currentis equiperiodie with the secondary current, and the whole a mined by thetime derivative of the. priE generated in the secondary, for the mostefticlent operation of the system the primary-currentrush should have adefinite relation as to period of recurrence and phase with respect tothe secondary oscillations. This requirement is answered by two conditions of tuning or timing the recurrenceperiod of the primary to theoscillation period of the secondary; to wit;

.First. An adjustment of the constants of the primary circuit so thatits natural time period (when the discharge-gap is short circuited, orreplaced by a non-rectifying gap) is about 117 times the natural periodof the oscillations or" the secondary. Fig. 6 approximately shows theresulting timerelation between the recurrent rectified primary impulsesand the secondary oscillations. This figure shows the fact that theprimary discharge .(l) lasts for a time about equal to one completedouble swing 1 of the secondary current (shown by sine curve), and thatthe wave-form of the pri mary discharge current plotted against time issuch that its time derivative is nearly of the same period as thesecondary current. It is to be observed that this is vnot to say matterwill be best understood by considera tion of the following statement offacts. The primary current is in theform of impulses practicallyunidirectional. When the primary current is'increasing, it impresses anelectromotivelforce on the secondary in one direction, and when theprimary current isdecreasing it impresses the electromotive force, onthe secondary, 'in the op: posite direction. This is. an efiectdetertion frequency. adjustment -ment1on mary current. 7 Therefore whilethe timerequired for the current of the discharge im-' pulse starting atzero to again become zero is greater than one-half the complete period(double swing) of an oscillation in the 0sc illation circuit (beingslightly less than the time of one complete double swing), never-vtheless the electromotive force impressed thereby on the oscillationcircuit has a he quency substantially the same as the natural frequencyof the oscillation circuit. The natural period of the currentoscillation of the primary circuit as determined by its inductance andcapacity, or as determined by measurements, it the gap hereof wereshort-circuited or replaced by an ordinary by the primary current wavemay he'made to have a derivative with respect to time in such form as toexcite oscillations in the secondary; while thejtime derivative of thesecondary current is of such form as not to be of proper period toexcite oscillations in the primary and therefore obviates return ofenergy to the primary circuit. The effect of the secondary current inits reaction on the primary is very difierent from its efiect if the twocircuits were equiperiodic. in the latter case the oscillatory secondarycurrent would give an oscillatory electromotive force in primary and ifthe primary were periodic and of the same period as the sec- -,ondary,the primary would be excited by thesecondary'and would take energy awayI from the secondary. By havingthe pri- *mary detuned .or of difierentper od from that of the secondary, asherein described,

the primary is rendered immune from ex- -cessive secondary reactions andconsequent waste of energy in the primary. The sec ondary reaction onthe primary is so small as'to have eiiect only when the primarycondenser is recharged from the source and is just ready to redischarge,and then the slight reaction of the secondary is sufiicient toprecipitate the primary discharge in proper phase to add energy to thesecondary circuit.

Second. An adjustment of thesupplycurrent and primary condenser so thatthe tre- .quency of primary impulses'is a submulti ple (1/2 to l/ie) of.the secondary oscillaa (Figs. 6, 7.) The second is notimportant when alarge number of secondary oscillations intervene between successiveprimary impulses, that'is: when n in the fraction l/n is large; but isimportant when n equals 2 or 3, or, a small number of secondaryoscillations intervene between primary 1m pu s 'Under such conditions oftiming, 'the phase-relation between the primary impulses and secondaryoscillations adjusts v breaking down point of the discharge-gap,

one of these ripples will supply just enough increment to serve as a'trigger, precipltating the discharge at the precise instant in relationto the secondary phase which is suited to the effective reception in thesec- 1 ondary of the excitation from the primary "impulse, which comesin to boost the secondary oscillation, and is extinguished beforearriving at a phase relation which would retard the secondaryvoscillation. -It is thusclear, that if the primary discharge frequencyis very low, referred to the secondary oscillation frequency, thepotential impressed by the condenser cannotrise fast enough to breakdown the gap at a minimum of potential-ripple induced by the secondary,-but must discharge on a ripplemaximum, whereas if the primarydisfcharge frequency is high, say: 1/2 or 1/3 the secondary oscillationfrequency, the rise of potential impressed by the condenser must becorrespondingly steep; so steep infact, that a discharge might'occur ata minimum' of induced potential ripple if the discharge frequency werenot timed-as above described.

What I claim and desire to'secure by Lets p tainedoscillation's aremamtamed, an exeltters Patent is 1. Means'for producing electrical0801113 tion's, .which comprises an exciting'circmt citing circuit beinand a radiating circuit receivingthe resultingrectified current-pulsesand having oscillations of its own natural period set up in it thereby;the conditions of the supply-current and of the condenser being suchthat the frequency of primary impulses is a'submultiple of the naturalperiod of the radiating circuit.

3. Means for producing electrical oscillations, which comprises anexciting circuit containing a charging condenser, and containing also adischarge-gap constructed and operating to rectifythecondenser-discharges; and a radiatingcircuit receiving the resultingrectified current-pulses and having oscillations of its own naturalperiod set up in it thereby; the constants of the exsuch that itsnatural I period, exclusive 0 the resistance differed tial of thedischarges, is about one and seven tenths times that of the radiatingcircuit; and the conditions of the supply-current and of the condenserbeing such that the frequency of primary impulses is a submultiple ofthe naturalperiod of-the radiating circuit. V v

4. Means for producing single-period oscillations in an electric waveradiator, which comprises a source of. supply-current, and

- an exciting circuit coupled to such radiator and including a"rectifying discharge gap,

the gap-structure being provided with means for removing discharge-heatfrom the gap-terminals; the supply-current and exciting circuit beingconditioried'to permit radiator-oscillations to precipitate succssivegap-discharges of lower frequency than the radiator-oscillations but inphase to boost the latter, and to'extinguish said gap discharges beforeoccurrence of a phase-relation retarding radiator-oscillations.

5; An apparatus for producing sustained electrical oscillationshaving,in comblna tion, an oscillation circuitin-which the'suslng circuitcoupled with the oscillation circult, acondenser in the excitingcircmt,a

A containing a charging condenser, and c(u1- -\supply,-circuit forcharging, the condenser,

taining also a discharge-gap constructed and operated to rectify thecondenser discharges; and a radiating circuit receiving .the' resultingrectified current-pulses and having oscillations of its own naturalperiod set up in it thereby; the constants of the exciting circuit beingsuch that its natural time-period, exclusive of the resistancedifferential of the discharges, is about one and -supply, an excitingcircuit containing. a

chargmgcondenser and containing also a discharge-gap which isconstructedand opcrates to rectify the condenser-discharges,

and -aldischarge gap the exciting circuit for permi g singleunidirectional/current discharges hrough the 'excitingpircuit,

said oscillation circuit reacting on the exciting circuit to causeripples of inducedelectromotive force therein which; serve to triggeroff the discharge in proper timed relation to the oscillations in theoscillation circuit so as to maintain and the de-- cliningoscillations.- i

6. An apparatus for producing sustained electrical oscillations having,111" combina--.

tion, an oscillation circuit in which'the sustained oscillations aremaintained, means for maintaining said oscillations comprising anexciting circuit, a. condenser in the exciting circuit, a discharge gapin-the exciting circuit, means for charging the condenser at such a ratethat the condenser does not receive a charge suflicient to break downthe discharge gap until after at least one complete oscillation in theoscillation circuit has taken place since the end of the precedingdischarge, said oscillation circuit reacting on the exciting circuitwhile the condenser is receiving its charge to cause induced ripples ofelectromotive' force across the discharge gap to trigger ed thedischarge in such relationship with the oscillations as to maintain andamplify the declinoscillations in the oscillation circuit.

An apparatus for producing sustained oscillations having, incombination, an oscillation circuit in which the sustained oscilla tionsare maintained, and means for maintaining such oscillations comprisingan exciting circuit coupled with the oscillation circuit and meanscooperating therewith for producing in the exciting circuit currentimpulses the duration of which is greater than one-half the completeperiod of the oscillations in the oscillation circuit'and which recur attime intervals which are integral multiples of the time period of theoscillations in the oscillation circuit and which impress on theoscillation circuit an electromotive force of a frequency substantiallythe-same as the natural frequency of the os cillation circuit,

8. An apparatus for producing electrical oscillations having, incombination, an oscillation circuit containing inductance and capacity,an exciting circuit coupled with the oscillation circuit and containinginductance, a condenser and a dischargegap, a supply circuit forcharging the condenser at such a rate that the'condenser does notreceive a charge suflicien't to break down the discharge gas until afterat least one com I plete oscillation in the osclllation circuit hastaken place since the end of the preceding arranged to extinguish thecondenser dis to charge after a single uni-directional disthat of theoscillation circuit, a. supply cir-- cuit for V charging o the condenserand condenser discharge, the capacityv andvinduc tance in the excitingcircuit being proportioned to cause a discharge, wave in the ca citingcircuit of greater wave length than the oscillations in the oscillationcircuit, said discharge gap, in conjunction with the absorption ofenergy from the exciting circuit by the oscillation circuit durin thecondenser discharge, being constructe and charge wave has taken place.

9. An apparatus for producing electrical] oscillations having, incombination, an os- C1llal31011 circuit contalnmg inductance andcapacity, an excitlng circuit containing inductance and a condenser anda discharge gap, coupled with'the oscillation circuit and having anatural time period greater than operating with the exciting circuit toproduce therein current discharge waves of a duration greater thanone-half that of the complete period of the oscillations in theoscillation circuit but of such form as to impresson the oscillationcircuit an electromotive force of a frequency substantially the same asthe natural frequency of the oscillatlon circuit and thereby exciteoscillations in the oscillation circuit of the natural oscillationperiod of said circuit.

10. An'apparatus for producing electrical oscillations having, incombination, an oscillation clrcult containlng inductance and capaclty,a'n exclting clrult contalnlng lnductance and a condenser and adischarge gap,

coupled with the oscillation circuit and having a natural time period ofoscillation of about 1.7 that of the oscillation circuit and operatingin conjunction with the oscillation circuit to cause the condenserdischarges taining condenser and coupled with the 0s.

cillation circuit and means coiiperating therewith for producing in theexciting condenser discharges for which the time required for, thecurrent starting at zero to again become zero is greater than one-halfthe complete'period of the oscillations in the oscillation circuit andof such a wave shape as to impress on the oscillation circuitelectromotlve force of substantially the same period as theoscillations.

12. An apparatus for producing sustained electrical oscillations having,in combination, an exciting current including inductance and capacityand a discharge gap, an oscillating circuit coupled with the excitingcircuit and containing inductance and capacity, a supply circuit forcharging the .condenser in the exciting circuit, said supply circuitserving to charge the condenser so that it discharges across thedischarge gap before the oscillations in the oscillation 1 cirjcuit diedown, the oscillations in the oscillation circuit serving to impressripples of electromotive'force upon the exciting circuit to triggerofithe condenser discharge in a predetermined phase relation to the saidoscillations, the inductance and capacity in the exciting circuit beingproportioned so as to produce a discharge wave in the exciting circuitof greater duration than one-r" induced, and an exciting circuit coupledwith the oscillation circuit and means cooperating therewith forproducing in the excitin circuit current impulses for which the timerequired for the current starting at zero to again become zero isgreater than one-half the complete period of the oscillations in theoscillation circuit and of sucha wave shape as to impress on theoscillation circuit an electro-motive force of substan- I discharge,the. capacity and, inductance in tially the same period as theoscillations. J v 14. An apparatus for producing electrical oscillationscomprising an oscillation circuit, and an exciting circuit andmeanscooperating. therewith for causing in the excitingcircuit currentimpulses of a duration about equal to one complete oscillation intheoscillation circuit but having a wave form such as to impress on theoscillation circuit an electromotive forceof about the same-pe-.

riod as the oscillations to be produced:

15 An apparatus for producing electrical oscillations having, ,incombination, an os cilla'tioncircuit, an exciting circuit coupled withand out of tune with the oscillation circuit, and means for causing inthe exciting circuit current impulses of a form such as to impress onthe oscillation circuit an electro'-- motive force of substantially thenatural 0s;

cillation period of 'said oscillation circuit,

the detunmg of the circuits serving to elfec tively hinder a re-transferof energy from the oscillation circuit to the exciting circuit.

16. An apparatus for producing electrical oscillations comprising anoscillation circuit, an exciting circuit coupled therewith but having aconsiderably dJfierent natural tune eriod, and means coiiperating there-WIth' or causin in theexciting circuit cur rent impulses 0 such a waveform as to impress on the oscillation circuit an electromotive forcehaving substantially the natural-period of the oscillation circuit.

17. An' apparatus for. producing sustained. electrical oscillationscomprising an oscillation circuit, an exciting circuit coupledtherewith, and means cocperating therewith for l g cu1t,t e oscillationcircuit reacting on the exciting circuit to trigger oil thecurrent-impulses 1n proper phase relation to maintain and amplify thedeclining oscillations. 18. An apparatus for producingelectricaloscillations comprising an oscillation circuit and an exciting circuitcoupled therewith, and means for causmg n the exciting circuit currentimpulses in the exciting circurrent impulses of such a wave form as to19. An apparatusfor producing electrical I oscillations having, incombination, an oscillation circuit containing inductance and capacity,an exciting circuit coupled with the oscillation circuit and containinginductance, a condenser and a discharge gap, a supply circuit forcharging the condenser at $110 rate that the condenser does not receivea charge sufiicient to break down the discharge gap until after atleastone complete-'oscillation in the oscillation circuit has taken placesince the end of the preceding condenser the exciting circuit beingproportioned to cause a discharge impulse in the exciting circuit of agreater duration than one half the complete period of the oscillationsin the oscillation circuit, said discharge gap in conjunction with theabsorption of energy at I from the exciting circuit by the oscillationcircuit during the condenser discharge, be-

ing constructed and arranged to quickly extinguish the condenserdischarge.

20. The method of producing electrical oscillations in an oscillationcircuit which consists in setting up in an exciting circuit coupled withthe oscillation circuit discontinuous current lmpulses, and causing theoscillations in the oscillation circuit to react on the exciting circuitto trigger ofi the current impulses in proper timed relation to theoscillations in the oscillation circuit to maintain and amplify thedeclining oscillations. v i

21. The method of producing electrical oscillations which consistsininducing a series of oscillation-exciting electro-motive forces bymeans of discontinuous unidirectional current impulses having a durationgreater than one-half the complete period of the oscillations sought tobe. produced,

and applying such electro-motive forces to a circuit containinginductance and capacity .to set up free oscillations therein.

- 22. The method of producing electrical oscillations which consists ingenerating current impulses of a duration considerably greater thanone-half the complete period of the oscillations sought to be producedbut of a form such as to induce an electro-motive force of substantiallythe same period electromotiye forces to an oscillation circuit, and inextmguishm the current impulses before the induced e ectro-motive forcear-;

rives at a phase relation suchflas to mate; .I'ially retard theoscillations.

electrical oscillations which consists in im- Signed by me at Boston,Massachusetts,

pressing exciting impulses on an oscillation this first day of November,1911. circuit and -in causing the oscillations to re- 1 act on theexciting impulses so as to cause EMORY LEON GHAFFEE' c the impressedimpulses to recur at time in- Witnesses: tervals which are integralmultiples of the ODIN ROBERTS, time period vof the oscillations. CHARLESD. WOODBERRY;

